The present disclosure is directed to adjusting a gain of a detector.
A photomultiplier tube (PMT) detector may have a photodetector (e.g., a photomultiplier tube, PMT) and a crystal, which is widely used in a nuclear detection field and a nuclear medicine field. For example, the photomultiplier tube detector may be applied to an experimental study of astrophysics, a container inspection, a Positron Emission Computed Tomography (PET), a Single Photon Emission Computed Tomography (SPECT), and the like. The crystal may be used to detect a photon (e.g., a γ photon) released from a detected subject and convert it into a visible light. The photodetector may be used to convert the visible light into an electrical signal.
The PMT may include an incident window, a photocathode, a multiplier system (a gate and a dynode), an anode, etc. The visible light (such as, a fluorescence) produced by a crystal array may emit onto the photocathode through the incident window of the PMT, and thus a photoelectric effect may occur and electrons may be accordingly generated. The electrons may be progressively multiplied by the dynode of the photomultiplier tube, and then collected by the anode to form an electrical signal. The detector may adopt a certain number of PMTs combined with dozens of times the number of crystals (also called a crystal array) to jointly perform a position detection of a γ photon annihilation point. A light guide may be used to split lights, and a centre-of-gravity method may be used to process the electrical signal formed by the PMT in order to acquire a position information of the γ photon annihilation point, so as to reconstruct an image based on the acquired positioned information. Hereinafter, the method may be also referred to as a centre-of-gravity based imaging method. The gains of different PMTs may be different from each other due to factors like their own performances of the PMTs. Thus, for optical signals of the same energy, the electrical signals outputted through different PMTs may be of different energy, which may cause calculation errors in position information and/or time information. Therefore, a gain adjustment may be performed on the electrical signals outputted by the PMTs in order to reduce a probability of calculation errors.
NEUSOFT MEDICAL SYSTEMS CO., LTD. (NMS), founded in 1998 with its world headquarters in China, is a leading supplier of medical equipment, medical IT solutions, and healthcare services. NMS supplies medical equipment with a wide portfolio, including CT, Magnetic Resonance Imaging (MRI), digital X-ray machine, ultrasound, Positron Emission Tomography (PET), Linear Accelerator (LINAC), and biochemistry analyser. Currently, NMS' products are exported to over 60 countries and regions around the globe, serving more than 5,000 renowned customers. NMS's latest successful developments, such as 128 Multi-Slice CT Scanner System, Superconducting MRI, LINAC, and PET products, have led China to become a global high-end medical equipment producer. As an integrated supplier with extensive experience in large medical equipment, NMS has been committed to the study of avoiding secondary potential harm caused by excessive X-ray irradiation to the subject during the CT scanning process.